Arc regulator apparatus



Dec. 16, 1952 w. o. BUCKINGHAM 2,522,223

ARC REGULATOR APPARATUS Original Filed Aug. 10, 1949 INVENTOR ATTORNEY Patented Dec. 16, 1952 ARC REGULATOR APPARATUS William D. Buckingham, Southampton, N. Y., assignor to The Western Union Telegraph Company, New York, N. Y., a corporation of New York Original application August 10, 1949, vSerial No.

, 109,456, now Patent No. 2,541,028, dated February 13, 1951. Divided and this application December 21, 1950, Serial No. 202,069

'7' Claims.

This invention relates generally to improved means for magnetically controlling arc discharge devices, and more particularly to suitable arc regulator apparatus for determinin and maintaininga desired spacing between electrodes, and a desired positionin 'of the are on the active surfaces of the electrodes, in concentrated-arc discharge lamps of the typedescribed in Buckinghamand Delbert Patent No. 2,453,118, which opcrate with a highlyconcentrated arc discharge in contradistinction to a low pressure diffused or glow discharge, the disclosure of which patent is incorporated herein by reference thereto.

This application is a division of application Serial No. 109,456, filed August 10, 1949, now Patent No. 2,541,028, issued February 13, 1951.

With suitable construction, such as illustrated herein, a concentrated arc device of the foregoing type is particularly adapted for use in high wattage lamps, such as those used in flood lamps, search lights and the like, operating in the open air and powered from a source of alternating current supply. The lamp utilizes two electrodes, which in an alternating current type operate as anodesandcathodes during each cycle of the alternating current supply which may be the l volt; 60 cycle current commonly available. Each of the electrodes may comprise a generally cylindrical metal'tube or shell that is closed at one-end and is filled with the electrode material. The thin active'surface film of the electrode material at the open end of the tube comprises a molten-metal, such as zirconium or hafnium, when the lamp is in operation, and underlying this active surface film isan oxide of the metal.

Thisoxide has a melting point much higher than thatof: the base metal which has high electron emissive'properties at the very high temperature at whichithe device operates, but which is not a sufiicientlygood electron emitter at lower temperaturesto cause theelectrons to be emitted'in sufiicient quantity to support an arc of high cur-'- rent density until the metal has reached incandescent temperatures, well above the melting point of the metal,

Either zirconium or hafnium-metal is a better electroniemitter at high temperatures than is its oxide, and it also has a lower melting temperature; thus, under the intense ionic bombardment of the are a very thin molten film of this metal is formed over the active surface area of the electrode, and as soon as it is formed the temperature of the electrode drops slightly and the underlying oxide solidifies and supports the film of molten metal on its surface. It is this thin 2 film of molten metal that is the chief source of the visible radiation from the lamp. It is so thin that surface tension holds it to the oxide backing so that the lamps may be burned in any position.

An important feature of the electrode structure isthat the lamp may be operated in the open air, and when thus operated the voltage drop across the lamp is within the range of 50 to 150 volts depending upon-the magnitude of the current flowing" through the lamp and the length of the arc gap, thereby substantially reducing the losses heretofore occasioned in ballast resistors of the size required with lamps having comparatively low voltage drops and operating from a 110 volt source of supply. In addition, thebrightness of the lamp is greatly increased when operatin in air; a, zirconium metal lamp in air produces from to 132 candles per square millimeter of active surface area, depending upon the size of the lamp, which is approximately twice the brightness of a zirconium oxide concentrated arc lamp operating in an envelope with a gas filling of argon and the like. The same effects and advantages are present with powdered hafnium metal as the electrode material and operating in air; a 25 watt lamp has a bril liance of 172 candles per square millimeter of active surface area, compared to 100 candles with hafnium oxide operating in argon.

The electrodes of the lamp slowly erode at their active ends during operation, but a portion of the zirconium or hafnium which is exposed to the arc oxidizes thereby to maintain the oxide layer which underlies and supports the film of vmolten metal on the surface of the electrodes. Each electrode may be as long as desired, for example, several inches long in the large size lamps, thereby to compensate for the burning of the active end of the electrode.

Although the-rate of erosion of the electrodes is very low, it is desirable to provide means for automatically maintaining the adjacent active surfaces of the electrodes at their proper spacing during operation of the lamp, and also to automatically move the electrodes towards each other to facilitate starting of the lamp and to move them away from each other to the proper spacing as soon as the lamp has started. A suitable spacing between the adjacent ends of the'electrodes generally is from one to two times the outside diameter of the electrode.- It was attempted to employ balanced voltage-current solenoids for maintaining the correct distance between the electrodes, but the non-linear char-' acteristics of the solenoids resulted in inaccurate control, and their massive armatures produced hunting problems which were difficult of solution. It is also desirable in certain instances to provide means for automatically rotating the electrodes about their longitudinal axes to insure proper centering of the light spots in their active surface areas.

One of the objects of the invention is the provision of more suitable means for automatically determining and maintaining a proper spacing between the adjacent ends of the electrodes of the arc discharge device, which means will automatically move the electrodes towards each other to facilitate starting the lamp and then move the electrodes away from each other to their proper spacing when the lamp has started.

Another object is to provide suitable control means for automatically maintaining a proper spacing between the electrodes, without having the control mechanism in the field of projection of the light.

A further object is to provide suitable means in combination with the automatic spacing means for automatically rotating the electrodes relative to each other about their longitudinal axes to insure proper centering of the light spots in their active surface areas.

Other objects and advantages of the invention will be apparent in the following detailed description of an illustrative embodiment thereof, taken in connection with the accompanying drawings in which:

Fig. 1 is a view, in elevation, of a high wattage open air lamp adapted to be powered from alternating current, in which the electrodes are mounted approximately at right angles to each other, with improved means for automatically determining and maintaining the correct distance between adjacent ends of the electrodes, the figure also showing means for rotating the electrodes about their longitudinal axes;

Fig. 2 is a fragmentary view, taken along the line 2--2 of Fig. 1; and

Fig. 3, shows a circuit arrangement for operating the alternating current lamp illustrated in l with means for automatically determining and maintaining the correct distance between the electrodes, and including means for automatically controlling the position of the arc tr am- Referring to Figs. 1 and 2 of the drawings. there, is shown a construction adapted for use with high wattage lamps, capable of operating in the open air and powered from a source. of alternating current supply. The lamp utilizes two electrodes I 2, which may be identical in construction if desired, and which alternately operate as anodes and cathodes during each cycle of the alternating current supply. The electrodes, may be disposed in axial alignment with each other, or may be disposed at an angle of approximately ninety degrees to eachv other, as, shown in Fig. 1,, in order to provide an unobstructed light output from the lamp. The light, which principally comes from the active surfaces t6, passes through a condenser lens 44 and thence through a light aperture 45 and projecting lens 46.

The interior construction of each of the electrodes preferably is in accordance with that disclosed in the parent case of which this is a division.

The electrode, material may comprise zirconior hafnium metal powder with which is 4 mixed a material that protects all but the active end of the core from oxidation, whereby progressive oxidation of the zirconium or hafnium metal beneath the underlying oxide layer can be prevented.

A suitable powdered metal, such as nickel, in the proportion of about one part of nickel to three parts of zirconium metal powder, when zirconium is employed, has been found to produce a mixture which does not progressively oxidize throughout its entire volume as would be the case if zirconium alone was used. Such electrodes acquire only a thin cap of zirconium oxide at the active end, and the underlying conductive nickel and zirconium mixture remains to aid in starting the lamps.

Preferably there is also added to the zirconium-nickel mixture a small percentage of metallic substance, such as magnetite, which is an oxide of iron, the magnetite increasing the electrical conductivity through the fused oxide cap when the electrode is cold, and thus aids in starting.

The exact proportions of the metals and oxides in the whole mixture do not seem to be critical. However, if more than 40% of nickel is employed in the mixture, excessive smoking occurs and the electrode erodes away more quickly; if less than 5% of nickel is employed, the protective action of the nickel is not pres ent. With respect to the conductive material. such as magnetite, from 2% to 1 5% may be em ployed.

As hereinbefore stated, each of the electrodes slowly erodes during operation of the lamp, and a portion of the zirconium which is exposed to the arc does oxidize thereby to maintain the underlying oxide layer, but further oxidation of the mass below the oxide layer does not take place to any substantial extent. The same effect is obtainable when hafnium metal powder is used instead of zirconium metal powder.

Each of the electrodes 12 is mounted in a holder [8 which is carried by a rotatable metal shaft. 23. Surrounding each shaft, and in goodelectrical contact therewith, is a metal collector block or collar 20 to which is secured, as by soldering or by screws, the external terminals 3 of the lamp. Each collector block is. secured to an insulating block 2| that is mounted on a s'lidable block 4'1, one of the blocks resting on the top surface of a cabinet or supporting frame 50, and

the other block 41. being mounted on a vertical' the electrodes are thereby rotated at suitable speeds about their longitudinal axes inopposite directions relative to. each other. This speed maybe quite; low, for example, one revolutionper minute, and should not be so, high, as to cause. appreciable centrifugal forces to be exerted on the active surfaces of the. electrodes or to cause rotation of the are: spot. A symmetrical oxide bead is thus formed and, maintained on each. electrode and the position of the luminous spot on each electrode is stabilized.

Fig. 1 shows the improved: means for automatically bringing the electrodes. together for starting the arc and for maintaining; them at a correct distance from each other during operation of'the lamp. The proper electrode-spacingoperation is based on a differential action between the arc voltage, 1. e., the voltage drop across the arc, and the arc current flowing at any instant. A satisfactory control is obtained by the use of a small two-phase alternating current motor 4| as the balance detecting unit. Each of the blocks 41 has a lug 48 which passes through a slot 49 in the frame structure 50, the lug 48 being internally threaded and receiving a threaded shaft 5|, and the shafts 5| are geared to each other through bevel gears 52. The shafts have right hand and left hand threads so that when the motor 4! turns in one direction, the block 41 and hence the electrodes will move towards each other, and when the motor reverses its direction the blocks and electrodes carried thereby will move away from each other. The motor advances the-electrodes until they touch and the arc is struck by a high voltage starting pulse, and when the arc current'is established the motor draws the electrodes apart to the proper operating distance and then stops. As hereinbefore stated, a suitable spacing between the electrodes is generally from one to two times the outside diameter of the electrode. As the electrodes slowly burn away, the control motor advances the electrodes to maintain their spacing and the relative positions of the luminous spots constant. The motor 4! is controlled in a manner hereinafter described in order to maintain the desired spacing between the electrodes.

It will be seen from Fig. 1 that when the electrodes are disposed at an angle to each other, the arc stream between the active surfaces l6 of the electrodes should follow a curved path, but sometimes the arc stream would tend to concentrate on the edges of the electrodes closest to each otheiyand at other times would tend to rise due to convection currents and also when the arc stream became too long. In order to prevent this there is provided an electromagnet comprising a coil 54 which is in series with the arc elec trodes of the lamp, and an electromagnet 55 which is bridged across the electrodes, these magnets being mounted on an insulating support structure 56 which is secured to the casing 50. The magnet 54, which is the current coil, is wound around a straight core 51 of magnetizable material, and the coil 55 is wound around a U-shaped cor of magnetizable material having projecting leg portions 58. The electromagnet 54, which is in series with the electrodes, may comprise for example 200 ampere turns for use with a 750 watt lamp, and the second electromagnet 55. which is connected across the electrodes may have for example 100 ampere turns. The current coil 54 is poled so that its external magnetic field tends to force the arc stream outwardly, whereas the voltage coil 55 is poled so that its external magnetic field tends to force the arc stream inwardly and keep the are from rising. The resultant field maintained by the two electromagnets operates to keep the arc stream centered on each of the active surfaces l8 of the electrodes and cause it to follow the curved path indicated by the broken lines in Fig. 1. Since the magnetic effect of one of the windings is proportional to the current flowing in the arc stream and, th magnetic effect of the oppositely poled winding is proportional to the voltage drop across the arc, the resultant effect of their magnetic fields tends to maintain the voltage-current relationship and hence the length of the are constant. This feature. relates to other divisible subject matter which is claimed in-my copending application Serial No. 177,612, filed August 4, 1950, now Patent No. 2,608,675, issued August 26, 1952.

Fig. 3 shows a starting and running circuit for the lamp, with means for automatically maintaining the proper distance between the electrodes in accordance with the instant invention. When the line switch 60 is closed, current is applied over. a circuit comprising conductors 6t and 64 to a high leakage reactance transformer 62 of the constant current type. The transformer shown is an auto-transformer, and con-' ductor BI is connected to the midpoint thereof so that if 110 volts of alternating current is applied to the primary part of the transformer, 220 volts will be generated across the secondary of the transformer. Bridged across the transformer is a vacuum switch 65, the switch being of the type in which the circuit is made and broken between solid contacts in a vacuum in response .to a mag-' netic field, such a switch having been found to be very effective to provide the surge required in' starting concentrated arc lamps of the type disclosed herein. The transformer 62 has an iron core and an open air gap and hence sets up a magnetic field which, when line switch 60 is closed,..attracts the magnetizable bar or armature 66 of the vacuum switch, opening the circuit formerly through the switch contacts, the latter circuit including the electrodes 12 of the arc lamp. Various kinds of such switches are.

well known; one particularly suitable for the purpose is disclosed in my copending application Serial No. 35,928, filed June 29, 1948, now Patent No. 2,564,877, issued August 21, 1951, the structure of which enables the switch to be mounted inan aperture in the core of transformer 62. Opening the circuit of switch causes a-surge of from 1000 to 2000 volts to appear across the electrodes [2 of the lamp, the surge being due to collapse of the field in the transformer 52, this circuit including a resistor 81' and the winding of electromagnet 54 which is a current coil such as referred to in the foregoing description of Figs. 1 and 2. When the gap between the electrodes I2 breaks down due to the voltage surge, the current flowing through transformer 62 from the supply line 68 maintains the arc across the electrodes and also keeps the contacts of switch 85 open so long as the lamp is operating.

Connected between one end of the transformer 62 and the electrode terminals is a transformer 70 through which the arc current flows. The secondary winding of the transformer 18 has a variable tap connection H, the upper end of the secondary winding being connected by means of a conductor 14 to one of the windings A of a two-phase motor, the other end of winding A being connected by a conductor 15 to the right-hand end of the transformer 62. The winding B of the two-phase motor 4| is connected across the supply conductors GI and 64, a condenser 13 being connected in circuit therewith in order to give a phase displacement so that there will be a suitable phase difference between the currents in the two windings A and B of the motor to provide the necessary startin torque for the motor.

The adjustable contact H on thesecondary winding of transformer 10 enables the voltage VI developed across the winding to equal the voltage V2 across the lamp terminals at the proper spacing of the electrodes. When voltage: Vii: equals voltage V2 the twoephase motor 41:- haslno voltage on one phase represented by winding A. Whenthe supply current is apthe are; The voltage vz then drops rapidly, and" the voltage-V I risestrapidly from. zero andlusually will be greater than V25. Under these conditions the motor 41 will' operate to separate the electrodes; to the correct. spacing as previou'sly determined: by." the: adjustment ofthe contact: H.

If the arcjspa'cing becomes tooxgreatthe voltage; V2: increases. and the current through the arc decreases: and hence; voltage VI. decreases, sojthatthere'is a difference betweenVl and V2 and this difference: causes currentv to" flow throughv winding A of the: motor and: causes: the motor to rotate; in, a direction to: bring. the electrodes towards each other. If'the' are spacin becomes too small, the voltage V2: decreases, and thexcurrentthrough the lamp and also the voltage VI increases, and the current. flow through winding? A ofv the, motor is opposite in.

phase: to that in the; previous case when the gap? was too long, so that, themotor will turn power, in; which case, one of the electrodes always operates an anode. The anode may com-- prise-a;-- plate; rod or other known, anode construction and, in fact;. may be a solid copper rodjwhichis of such, construction as to, prevent overheating and vaporization at the point'of arc contact-l While? there is shown and described herein one, illustrative, embodiment of the: invention,

many other and varied forms and" uses will present themselves to those versed in the art without departingfromtheinvention, and the invention is therefore not limited either in structure or in use except as indicated by the scope of the appended claims.

What is claimed is:

'1. arc discharge: device comprising elec-" trodes operating in a gaseous medium ata pressure;- sufiic'iently high tocause the discharge between the electrodes to assume the: shape oi aconcentrated arc, and regulating means for automatically" moving" said' electrodes towards and fromeach other to maintain a predet'er mined desiredarc" spacing between-- tlie'm during operation: of the device, said-regulating means comprising an alternating current reversible motor devicerotatable to advance or retract the electrodes, said motor device having? at: least two windings with a phase difference between the currentsfiowing in the windings; respectively, said windings being operatively connected to the arc: circuit so that the torque produced by the windings ispropcrtional to" the difference between avoltage which is proportional to the The arrangement thus.

current flowing; in the are: stream and: the volt age drop. across the arc, the: resultant torque" causing the motor device: to turnin a direction to maintain said predetermined desired are spacing: between the electrodes.

2; An arc discharge device comprising: electtrodes operating in a; gaseous medium at a pressure sufficiently high) to cause the discharge between the electrodes to assume the shape? of w a concentrated are, and regulating" means: for automatically moving. said electrodes: towards;

and" away from each other. to; maintain: a; pre.- determined desireda arc spacing between-them during operation? of the device,; said regulating;

means; comprising an: alternating. current: two-' phasereversible motor rotatable to" advance or retract: the electrodes; said motor having at le'ast two, windings, with a" phase difference between? in'gbetween. the; electrodes:

3 A113 arc discharge: device comprising elec-: trodes operating inaa gaseous-medium. ata pressure; sufficiently high to. cause the discharge be tween the electrodes to assume the: shape ofa.

concentrated-arc; andregulating meansuforautbmatically moving said electrodes; towardsv and: from each other to; maintain a predetermined de sired arc spacin betweenthem'during operation;

of the device, said regulating meansi comprising analternating current reversible-motor devicearo tatable to advanceor-retra-ct the electrodes, said motor deviceg havin-g at least two windings with; a phase dirlerence betweengthecurrents* flowingin the windings respectively, means for producing? at first voltage which is proportionalto the jcurrent flowing in the arcstream; and ,meanszffor'lproduc ing 3;; second voltage which is;;-proportional to? the difierence-between saidfirst voltageand; thBIVOlfl age: drop; across; the are; and for applying..said* difference voltage toone of: the windingszofii said? motor device, to cause: it to; rotate: a: direction: and to an extent to maintain; saidpredetermineddesired: are spacing: between the electrodes:

ii-An arc discharge; device? comprising: elec trodes operating in-a gaseousimediumiaatt a: pres"- sure suihcientlyhigh-to? cause the;-dischar-ge'v be?- tweemtheelectrodkrs to: assume the-"shape of w concentrated arc, and 'regulatingvmeansifor aut0- niatically moving saidelectrodes? towards: and

from eachvother to. maintain a predetermined de sired, arc spacing between; them: during: operationofthe" device,, said regulating means-corn prising analternating current reversibleimctor device rotatable-toil advance. or retract: the elec trodes,- said motor, device having at? least. two? windings with; a: phase difference" between-the currents: flowing in: the" windings respectively source of alternatin current. power su'p'pi motor windings: from said power supply; a t' former having. a primary winding connected said: Power supply: and in series with the" are? ingi: a: voltage; which represents the" voltage drop y fo thegarc discharge; means for energiZihg'One Of said' 9 across the arc, and means including said circuit connections and the secondary winding of said transformer for producing a second voltage which is proportional to the difference between said first voltage and the voltage drop across the arc and for applying said difference voltage to a second winding of said motor device to cause it to rotate in a direction and to an extent to maintain said predetermined desired arc spacing between the electrodes.

5. An arc discharge device comprising electrodes operating in a gaseous medium at a pressure sufliciently high to cause the discharge between the electrodes to assume the shape of a concentrated arc, and regulating means for automatically moving said electrodes towards and from each other to maintain a predetermined desired arc spacing between them during operation of the device, said regulatin means comprising an alternating current reversible motor device rotatable to advance or retract the electrodes, said motor device having at least two windings with a phase difference between the currents flowing in the windings respectively, a source of alternating current power supply for the arc discharge, means for energizing one of said motor windings from said power supply, a transformer having a .primary winding connected to said power supply and in series with the arc stream, means comprising the secondary winding of said transformer for producing a first voltage which is proportional to the current flowing in the arc stream, circuit means connectin one end of a predetermined portion of said secondary winding to one end of a second winding of said motor device and the other end of said portion of the secondary winding to one side of the arc, and circuit means connecting the other end of said second motor winding to the other side of the are, said predetermined portion of the secondary transformer winding and said circuit means producing a second voltage which is proportional to the difference between said first voltage and the voltage drop across the arc and applying said difference voltage to said second winding of said motor device to cause it to rotate in a direction and to an extent to maintain said predetermined desired arc spacing between the electrodes.

6. An arc discharge device comprising longitudinally-extending electrodes operating in a gaseous medium at a pressure sufiiciently high to cause the discharge between the adjacent ends of the electrodes to assume the shape of a concentrated arc, regulating means for automatically moving said electrodes towards and from each other to maintain a predetermined desired arc spacing between said adjacent ends thereof during operation of the device, said regulating means comprising an alternating current reversible motor device rotatable to advance or retract the electrodes, said motor device having at least two windings with a phase difference between the currents flowing in the windings respectively, means for producing a first voltage which is proportional to the current flowing in the arc stream, and means for producing a second voltage which is proportional to the difference between said first voltage and the voltage drop across the arc and for applying said difference voltage to one of the windings of said motor device to cause it to rotate in a direction and to an extent to maintain said predetermined desired arc spacing between the electrodes, and means for automatically rotating the electrodes relative to each other about their longitudinal axes to insure proper centering of the arc stream in the active surface areas of the adjacent ends of the electrodes, said rate of rotation being lower than that which would cause appreciable centrifugal forces to be exerted on said active surface areas.

'7. An arc discharge lamp comprising longitudinally-extending electrodes operating in a gaseous medium at a pressure sufliciently high to cause the discharge between the adjacent ends of the electrodes to assume the shape of a concentrated arc and produce highly incandescent light spots in the active surface areas of said adjacent ends, regulating means for automatically moving said electrodes towards and from each other to maintain a predetermined desired arc spacing between said adjacent ends thereof during operation of the lamp, said regulating means comprising an alternating current reversible motor device rotatable to advance or retract the electrodes, said motor device having at least two windings with a phase difference between the currents flowing in the windings respectively, means for producing a first voltage which is proportional to the current flowing in the arc stream, and means for producing a second voltage which is proportional to the difference between said first voltage and the voltage drop across the arc and for applying said difference voltage to one of the windings of said motor device to cause it to rotate in a direction and to an extent to maintain said predetermined desired arc spacing between the electrodes, and means for automatically rotating the electrodes in opposite directions relative to each other about their longitudinal axes to insure proper centering of the light spots in their active surface areas, said rate of rotation being lower than that which would cause appreciable centrifugal forces to be exerted on said active surface areas.

WILLIAM D. BUCKINGHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,615,687 Eschholz Jan 25, 1927 2,329,127 Levy Sept. 7, 1943 2,488,861 Gooch Nov. 22, 1949 

